1. Field of the Invention
The present invention relates to the art of information processing. It finds particular application in relational database systems accessed regionally, nationally or globally over the Internet or a wide area network, and will be described with particular reference thereto. However, the present invention is useful in enhancing accessibility of other types of databases to users over wide geographical areas.
2. Description of Related Art
Relational databases are widely used for storing, sorting, delivering, and otherwise processing large volumes of similar and/or dissimilar data. By combining the relational database paradigm with the Internet, a large corporate intranet, or other wide area network, large numbers of users can access database contents, or selected portions thereof, regionally, nationally, or globally. However, large numbers of users accessing a central database can create substantial bottlenecks which slow the database system, creating delays, timeouts, and other problems.
The use of application servers can reduce this bottleneck. The application servers process user requests by accessing the central database server. The application servers may include servers within a intranet, firewall, or other secure computing environment, and/or may include servers distributed across the Internet. These latter distributed application servers are also known as edge servers. In some cases, the edge servers do not directly access the central database server, but rather proxy database requests through an intermediate application server residing inside of the firewall. Application servers reduce bottlenecking at the central database by extracting database content in a portable format, such as a text file format, and inserting the extracted portable content into a remote database maintained by the application server.
While this approach is beneficial, some difficulties remain. Typically, the entire database contents are not efficiently converted to a portable format due to processing and communication constraints. Thus, the intermediate application servers frequently access the central database server to extract additional data to update the edge database or to satisfy user requests for additional data. Moreover, some data types may be incompatible with the selected portable format. For example, graphical images may be difficult to convert to a text format.
In another approach, data is archived, and the archive file is transferred from the central database server to the edge servers where it is unpacked or otherwise accessed. Advantageously, this approach can support substantially all data types. However, certain difficulties still remain. The archived content is unpacked and stored on the edge server in a native format which is typically specific to the edge server. Thus, the updating may require edge server-specific parameters such as identification of the storage medium, a file path, and the like. This edge server-specificity makes updating large numbers of edge servers difficult. In some existing database networks, tens of thousands of edge servers are supported by the central server, making server-specific updating burdensome.
Another problem arises with updating. Typically, the edge server in this approach is updated by generating an updated archive file at the central database server and transferring the updated archive file to the edge server. The unpacked contents of the previous archive file are invalidated, which causes open application connections to the edge server database to be closed. The applications are then restarted to establish connections to the updated edge server database. Closing the open application connections can create problematic interruptions in uncommitted transactions and can disrupt or terminate user sessions.
The present invention contemplates an improved method and apparatus which overcomes these limitations and others.